The present invention is directed to adhesives useful for seaming components useful in electrostatographic, including digital apparatuses. In specific embodiments, the present invention is directed to adhesives useful for components such as seamed belts, and more specifically, to endless flexible seamed belts wherein an image can be transferred at the seam of the belt with little or no print defects caused by the seam. In embodiments, the present invention relates to adhesives useful for seaming xerographic component imageable seamed belts, wherein the adhesive is formed between mutually mating elements of a seam, and wherein the adhesive comprises a resin, preferably with an electrically conductive filler dispersed or contained therein. In a particularly preferred embodiment, the resin is selected from polyvinyl butyral resins, phenolic resins, epoxy resins, and mixtures thereof. Preferably, the filler is an electrically conductive or semi-conductive carbon filler such as carbon black, graphite, fluorinated carbon, or mixtures thereof. The present invention further provides, in embodiments, an adhesive, which provides increased strength because the adhesive is crosslinked. Preferably, the adhesive provides a seam that is strong enough to survive mechanical flexing while under tension, as the belt travels over various diameter rollers. The present invention, in embodiments, also provides an adhesive, which when placed between seaming members of a belt, provides a seam in which the height differential between the seam and the rest of the belt is virtually nil. A belt having the adhesive, in embodiments, allows for image transfer at the seam, which cannot be accomplished with known seamed belts. Image transfer is accomplished partly because the present adhesive provides a seam that possesses the desired conductivity and release properties required for sufficient transfer. Image transfer is further made possible because the adhesive provides a seam that is virtually or completely free of bubbles, voids, and other inclusions, which may impact high quality image transfer at the seam region.
In a typical electrostatographic reproducing apparatus such as an electrophotographic imaging system using a photosensitive member, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member and the latent image is subsequently rendered visible by the application of a developer mixture. One type of developer used in such printing machines is a liquid developer comprising a liquid carrier having toner particles dispersed therein. Generally, the toner is made up of resin and a suitable colorant such as a dye or pigment. Conventional charge director compounds may also be present. The liquid developer material is brought into contact with the electrostatic latent image and the colored toner particles are deposited thereon in image configuration.
The developed toner image recorded on the imaging member is transferred to an image receiving substrate such as paper via a transfer member. The toner particles may be transferred by heat and/or pressure to a transfer member, or more commonly, the toner image particles may be electrostatically transferred to the transfer member by means of an electrical potential between the imaging member and the transfer member. After the toner has been transferred to the transfer member, it is then transferred to the image receiving substrate, for example by contacting the substrate with the toner image on the transfer member under heat and/or pressure.
Transfer members enable high throughput at modest process speeds. In four-color photocopier or printer systems, the transfer member also improves registration of the final color toner image. In such systems, the four component colors of cyan, yellow, magenta and black may be synchronously developed onto one or more imaging members and transferred in registration onto a transfer member at a transfer station.
In electrostatographic printing and photocopy machines in which the toner image is transferred from the transfer member to the image receiving substrate, it is desired that the transfer of the toner particles from the transfer member to the image receiving substrate be substantially 100 percent. Less than complete transfer to the image receiving substrate results in image degradation and low resolution. Complete transfer is particularly desirable when the imaging process involves generating full color images since undesirable color deterioration in the final colors can occur when the color images are not completely transferred from the transfer member.
Thus, it is desirable that the transfer member surface has excellent release characteristics with respect to the toner particles. Conventional materials known in the art for use as transfer members often possess the strength, conformability and electrical conductivity necessary for use as transfer members, but can suffer from poor toner release characteristics, especially with respect to higher gloss image receiving substrates.
Polyimide substrate transfer members are suitable for high performance applications because of their outstanding mechanical strength and thermal stability, in addition to their good resistance to a wide range of chemicals. However, the high cost of manufacturing unseamed polyimide belts has led to the introduction of a seamed belt.
In the electrostatic transfer applications, use of a seamed transfer polyimide member results in insufficient transfer in that the developed image occurring on the seam is not adequately transferred. This incomplete transfer is partially the result of the difference in seam height and the rest of the belt. A “bump” is formed at the seam, thereby hindering transfer and mechanical performance. The development of puzzle cut seams has increased the quality of transfer somewhat, by decreasing the seam height, thereby allowing smooth cycling. However, even with the improvements made with puzzle cut seams, quality imaging in the seamed area is not obtainable at present due, in part, to contrast in transfer caused by differences in electrical and release properties of known seaming adhesives. Further, current adhesives do not provide sufficient bonding strength at the seam, resulting in short belt life. In addition, the seam must have the appropriate surface properties in order to allow for sufficient toner release at the seam.
Currently, puzzle cut seam adhesives consist of insulating ultraviolet-curable epoxies and hot-melt adhesives. While these adhesives exhibit acceptable strengths at room temperature under tensile load, most undergo premature failure at elevated temperatures. Additionally, the existing adhesives have been found to perform poorly under some important dynamic test conditions.
Therefore, it is desired to provide a more robust adhesive system useful to seam puzzle cut seamed belts. Further, it is desired to provide an adhesive having electrical, mechanical and toner release characteristics that closely match those of the robust substrates. In addition, it is desirable to provide a seam, which is imageable, thereby reducing or eliminating the presence of print or copy defects. Also, it is desired to provide an adhesive, which when placed between seaming members of a belt, provides a seam in which the height differential between the seam and the rest of the belt is virtually nil. Moreover, it is further desired to provide an adhesive which provides a seam that is virtually or completely free of bubbles, voids and other inclusions, which may impact high quality image transfer at the seam region.
U.S. Pat. No. 5,549,193 relates to an endless flexible seamed belt comprising puzzle cut members, wherein at least one receptacle has a substantial depth in a portion of the belt material at the belt ends.
U.S. Pat. No. 5,721,032 discloses a puzzle cut seamed belt having a strength-enhancing strip.
U.S. Pat. No. 5,487,707 discloses a puzzle cut seamed belt having a bond between adjacent surfaces, wherein an ultraviolet cured adhesive is used to bond the adjacent surfaces.
U.S. Pat. No. 5,514,436 relates to a puzzle cut seamed belt having a mechanically invisible seam, which is substantially equivalent in performance to a seamless belt.